Photonic signals are widely used for data processing and communications applications. As is well known to those having skill in the art, photonic signals include electromagnetic signals such as optical signals, x-ray signals and microwave signals. Because of their enhanced properties compared to conventional electrical signals, photonic signals are widely being investigated as replacements for electrical signals in data processing and communications applications. Thus, for example, optoelectronic devices are replacing conventional electrical devices, and optical interconnections are replacing electrical interconnections in data processing systems.
A major building block of a system which uses photonic signals is a delay block. Low distortion, controllable delays are generally required to synchronize photonic signals. Moreover, a delay apparatus and method is also required for applications such as information processing, phased array antennas, information routing, and other applications in the telecommunications, commercial, consumer and military fields. For example, phased away antennas must be increasingly agile which places even greater demands upon the precision and controllability of photonic signal delays.
A high quality delay apparatus and method should provide a large, controllable delay for short photonic pulses. In particular, for a photonic pulse signal having a predetermined frequency and a predetermined bandwidth, it is desirable for the delay apparatus and method to provide a controlled amount of delay at the predetermined frequency, and which is uniform across the signal bandwidth. Accordingly, photonic signals at the predetermined frequency and having the predetermined bandwidth can be passed through the delay apparatus substantially unaltered, while imparting the predetermined delay to the signals.
Moreover, as electronic systems become more compact and lightweight it is important for the photonic delay to be implemented in a compact, lightweight apparatus which is compatible with other integrated optoelectronic systems. The apparatus should be easy to manufacture using conventional techniques and should be operable with signals of virtually any frequency.